ARM Template Parameters, Variables, and Outputs

Parameters, variables, and outputs make ARM templates flexible and reusable. Parameters accept input at deployment time, variables simplify repeated expressions, and outputs return values after deployment. In this lesson, you will learn how to use all three effectively.

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Parameters

Parameters allow you to provide values when deploying a template. This makes templates reusable across environments.

Defining Parameters

{
  "parameters": {
    "environment": {
      "type": "string",
      "allowedValues": ["dev", "staging", "prod"],
      "defaultValue": "dev",
      "metadata": {
        "description": "The deployment environment"
      }
    },
    "vmSize": {
      "type": "string",
      "defaultValue": "Standard_B2s",
      "metadata": {
        "description": "Size of the virtual machine"
      }
    },
    "adminPassword": {
      "type": "securestring",
      "metadata": {
        "description": "Administrator password for the VM"
      }
    },
    "instanceCount": {
      "type": "int",
      "defaultValue": 2,
      "minValue": 1,
      "maxValue": 10,
      "metadata": {
        "description": "Number of VM instances"
      }
    },
    "enableDiagnostics": {
      "type": "bool",
      "defaultValue": true
    },
    "tags": {
      "type": "object",
      "defaultValue": {
        "project": "webapp",
        "costCentre": "12345"
      }
    }
  }
}

Parameter Types